1. Field of the Invention
The present invention is relating to an electrical connector plug for ignition devices including a housing and a plug-in projection mold onto the housing in combination with a shielding device. Such plugs find particular application for airbag restraint systems in motor vehicles.
In airbag restraint systems, the plug connector with its plug-in projection is plugged onto a corresponding counterpart which is located on the housing of the ignition device of the airbag. The ignition device, the impact bag as well as the electrical leads are located on the driver""s side in the impact plate of the steering wheel. Furthermore, the electrical connection of the ignition device forms, together with the control system, a very sensitive place of the restraint system, since uncontrolled potential fluctuations which occur on the electrodes of the ignition device may lead to an unscheduled release of the airbag.
2. Description of the Prior Art
The U.S. Pat. No. 4,306,499, describes a plug connector with non-massed junctions. In order to provide a shield from electrostatic energy, an ignition initiator is fitted with a shield socket which surrounds an ignition unit, so that electrostatic energy received from the socket which is connected to the ignition unit is passed to the shield socket via a spark discharge. This prevents an uncontrolled triggering of the ignition device via electrostatic energy
This construction has the drawback that the ignition distance between the two sockets of the ignition device must be very carefully adhered to, which makes this the requirement placed on the process of manufacture of the two shells a very stringent one and this fact, in turn, is responsible for a very high cost of the ignition device as a whole. Furthermore, neither the electrical junctions of the ignition device, nor the electrical junctions of the plug connector are protected in any way. Thus, the ignition device or the plug connector can be electrostatically charged so that during the process of plugging in the electrostatic energy is sufficient to trigger the ignition device.
For this reason, known plug connectors have plug-in pins in their plug-in sockets which are plugged onto plug pins and the plug-in projection separates a shorting bar between the plug pins of the ignition device from the latter when the contact for the plug-in sockets already exists.
The said shorting bar effectively prevents the unscheduled triggering of the ignition device by electrostatic energy during the process of plugging-in.
The patent EP 0 591 947 describes a plug connector equipped with such a shorting bar which is so constructed that the shorting bar is arranged in an additional restraint.
This construction has the drawback that the plug connector now consists of three parts, to wit, the plug connector itself, the complementary matching plug-in counterpart and the restraint with a shorting bar. This increases costs as well as prolongs the time needed for carrying out the construction.
In both cases, the ignition devices are triggered via a control unit, where the ignition devices exhibit no xe2x80x9cintelligencexe2x80x9d, that is to say, they do not incorporate any control electronics. Therefore, a current is sent by the electronic control center to the ignition device, causing the latter to ignite.
The plug connectors which are here presented are not suitable for the linking of peripherals such as airbag igniters to the newly introduced bus systems which have recently been introduced into vehicle technology.
The present invention has the goal of connecting the ignition device carrier of the ignition device to mass immediately on being plugged in, even before the electrical pins of the ignition device and the electrical plug-in sockets of the plug connector have made electrical contact. Furthermore, the plug-in part of the plug connector should be protected from acquiring an electrostatic charge or from electromagnetic interference.
This goal is achieved by an electrical plug connector including a housing an a plug-in projection mold onto the housing which comprise along the plug-in direction of the plug connector contact elements for mating by a mating face with corresponding counter elements in a connector part wherein a shielding device includes an electrically conductive ring on the mating face which surrounds ends of the contact elements and with at least one connection which is connected to a cable in the plug connector.
The electrical plug connector fitted with a shielding device may exhibit a housing. Furthermore, a plug-in projection may be provided on the housing, which may exhibit cells distributed along the plug-in direction of the plug connector, in which contact elements may be located. On the side of the plug-in projection can be arranged at least one stop spring element which may also be a stop spring arm, for clicking into at least one retainer provided in a corresponding connector part which is complementary to the plug-in projection. Further, a guide element for sliding into a complementary piece may be provided. Apart from this, the connector plug may exhibit a cover which matches the housing. The shielding device may have an electrically conducting ring connected to mass which surrounds the contact elements which exhibit contact studs distributed around the plug-in projection.
In the case of the said electrical connector plug, the fact that the shielding device surrounds the insertion projection like a Faraday cage and is integrated in the connector plug is particularly advantageous. It is a special feature of the shielding device that it is arranged on the plug-in projection in such a way that on being plugged into a metal ignition device carrier, the latter is automatically earthed.